Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!rutgers!apple!bionet!agate!ucbvax!ucsfcgl!pixar!loren
From: loren@pixar.UUCP (Loren Carpenter)
Newsgroups: comp.arch
Subject: Re: The 3G Machine
Keywords: user-interface bandwidth
Message-ID: <2623@pixar.UUCP>
Date: 30 Oct 88 20:11:12 GMT
References: <470@oracle.UUCP> <3405@pt.cs.cmu.edu> <3440@pt.cs.cmu.edu> <471@oracle.UUCP>
Reply-To: loren@pixar.UUCP (Loren Carpenter)
Organization: Pixar -- Marin County, California
Lines: 46

In article <471@oracle.UUCP> csimmons@oracle.UUCP (Charles Simmons) writes:
>In article <3440@pt.cs.cmu.edu> ralphw@ius3.ius.cs.cmu.edu (Ralph Hyre) writes:
>>I believe that only 2-3 screens/person are needed, but remember you want 
>>24-bits/pixel, so its really 2kx2kx24 at 10 frames/second is the limit.
>
>Um...  I was kind of thinking that the 2Kx2Kx24 color screen would update
>at something like 40 to 60 frames per second.  Presumably that would
>require a bandwidth of something like 480 to 720 Megabytes per second.
>
>(The intent is to have
>a screen that has no artifacts.  The screen has to have resolution better
>than you can get in a theater.  I remember watching a movie once, and
>being bummed because updating a screen at only 24 or 30 frames per second
>makes candle flames jump around all over the place.)
>
>-- Chuck


You don't want artifacts?...

Well, first you have to quit thinking 24 bits (8 each RGB) is sufficient.
Of course, with perfectly matched and compensated dac's, monitors,
ambient lighting, etc. you might get away with 8 bits.  Also it's important
to distinguish the number of bit planes per color in the memory from the
number of bits going into the dac.  It's not hard to find examples where
10 in or 10 out are barely enough, especially as the dynamic range of
displays improves.  

The monitor frame rate had better be more than 60.  60-72 frames per
second is demanded by folks who look at imagery all day.

35mm projection resolution in a typical theater is roughly equivalent
to 1200-1500 horizontal lines.  70mm is not quite twice as good.
However, a projected film image jumps around with projector frame-to-frame
misalignment, has grain noise that averages out somewhat, is run through
a 2 (or 3) bladed shutter which flashes each frame twice (or 3 times),
and so on...   The multi-bladed shutter is responsible for the strobing
of the candle flame (as well as the strobing of non-motion-blurred animation).

Yeah, I'd like a 2kx2k (2kx3k would be better) 64-bit (16 each RGBA)
frame buffer with a 66 hz frame rate.  It's possible to build such
an animal today, but you couldn't sell it for less than $200k.


				Loren Carpenter
				...{ucbvax,sun}!pixar!loren